optics

build.sbt

@@ -41,6 +41,7 @@ lazy val model =
           Settings.Libraries.CatsTestkit.value ++
           Settings.Libraries.Circe.value ++
           Settings.Libraries.DisciplineMUnit.value ++
+          Settings.Libraries.Monocle.value ++
           Settings.Libraries.MUnit.value
     )
 

model/src/main/scala/clue/data/InputOptics.scala

@@ -0,0 +1,23 @@
+// Copyright (c) 2016-2023 Association of Universities for Research in Astronomy, Inc. (AURA)
+// For license information see LICENSE or https://opensource.org/licenses/BSD-3-Clause
+
+package clue.data
+
+import monocle.PPrism
+import monocle.Prism
+
+trait InputOptics {
+  final def pAssign[A, B]: PPrism[Input[A], Input[B], A, B] =
+    PPrism[Input[A], Input[B], A, B](_.toOption.map(Right(_)).getOrElse(Left(Ignore)))(Assign.apply)
+
+  final def assign[A]: Prism[Input[A], A] =
+    pAssign[A, A]
+
+  final def ignore[A]: Prism[Input[A], Unit] =
+    Prism[Input[A], Unit] { case Ignore => Some(()); case _ => None }(_ => Ignore)
+
+  final def unassign[A]: Prism[Input[A], Unit] =
+    Prism[Input[A], Unit] { case Unassign => Some(()); case _ => None }(_ => Unassign)
+}
+
+object optics extends InputOptics

model/src/main/scala/clue/data/syntax/package.scala

@@ -3,6 +3,10 @@
 
 package clue.data
 
+import monocle.PLens
+import monocle.POptional
+import clue.data.optics
+
 package object syntax {
   implicit final class AnyToInputOps[A](private val a: A) extends AnyVal {
     def assign: Input[A] = Assign(a)
@@ -12,4 +16,17 @@ package object syntax {
     def orIgnore: Input[A]   = Input.orIgnore(a)
     def orUnassign: Input[A] = Input.orUnassign(a)
   }
+
+  implicit final class LensToLensOps[S, T, A, B](private val lens: PLens[S, T, A, B])
+      extends AnyVal {
+    // Copied verbatim from monocle, which has it as a private member
+    private def adapt[A1, B1](implicit evA: A =:= A1, evB: B =:= B1): PLens[S, T, A1, B1] =
+      evB.substituteCo[PLens[S, T, A1, *]](evA.substituteCo[PLens[S, T, *, B]](lens))
+
+    def assign[A1, B1](implicit
+      ev1: A =:= Input[A1],
+      ev2: B =:= Input[B1]
+    ): POptional[S, T, A1, B1] =
+      adapt[Input[A1], Input[B1]].andThen(optics.pAssign[A1, B1])
+  }
 }